High tension impulse transformer



2 Sheets-Sheet 1 Filed Nov. 7, 1961 II 0 III July 13, 1965 K. WlLLUTZKl3,195,020

HIGH TENSION IMPULSE TRANSFORMER Filed Nov. '7, 1961 2 Sheets-Sheet 2 /NVE/vraQ 444% M fliola.

fl-TTORNE Y United States Patent 17 Claims. (Cl: 317-15162) Theinvention relates to a high tension impulse transformer for highmomentary output, particularly for generating high voltage sparks forigniting fuel/ air mixtures.

For more than 20 years efforts have been made to create an improvedignition with transformed condenser discharges. Of such condenserdischarging ignition arrangements the most important advantage expectedis the fact that these guarantee a safe ignition regardless of the stateof insulation of the spark gap.

This would remove one of the greatest disadvantages of the high voltage(battery or magneto) ignition used at present, namely the unreliableoperation, or the complete failure caused by the fouling of the ignitionspark gap by Water condensation, fuel condensation, oil and carbonaceousoil precipitates, which are unavoidable in some working conditions.

The reason that these ignition arrangements hitherto have not beenadopted in practice, may be due partly to the proposals for thestructural arrangement of the material employed and partly to improperapplication of the guiding principles which have not resulted inpractical serviceable ignition arrangements.

The object of the present invention is the production of an improvedhigh tension impulse transfer by means of which a practical serviceablecondenser discharging ignition arrangement is possible.

The light tension impulse transformer, according to this invention, isdistinguished by the combination of the following characteristics:

(a) The internal primarywinding is disposed on a tubular former with aradial externally arranged flange;

(b) The external secondary winding is disposed in a pot shaped former,which rests in contact with the free end of the primary coil former andsurrounds the pn' mary winding, the potshaped former having a dependingcylindrical projection which fits into the interior of the primary coilformer;

(c) The low voltage ends of the primary and sec ondary windings whichpreferably are both earthed, are near to the flange of the primary coilformer;

(d) The high voltage end of the secondary Winding, is arranged levelwith the base of the former and is led out through the dependingcylindrical projection.

The above mentioned construction has the substantial advantage that,despite a very compact mounting, a high resistance to breakdown issecured, because points in the winding at high potentials can only comeinto contact with points in the Winding at lower potentials along longleakage paths.

A further important advantage is that the high tension impulsetransformer described herein can be easily slid on to the insulatingbody of a spark plug and connected thereto.

The separate layers of the high voltage winding which is arranged inseveral layers, preferably have a lesser axial length than the primarywinding and are arranged in steps towards the high voltage end.

Each layer of the secondary winding thus extends only over part of theaxial length of the winding space, the unwound part being filled with apaperlayer the thicknessof which is similar to the diameter of the wire.

In order to avoid sparking or leakage from layer to 3,195,920 assentedJuly 13, 1965 ICC layer, layers in the second winding woundprogressively in the same axial direction, alternate with other layerswound progressively in opposite axial direction.

The primary winding of the high tension impulse transformer preferablyconsists of plain copper strip, which is wound with interposedinsulation in the form of a layer of insulating material on the former.The resistance of the primary winding should be less than the aperiodiclimit resistance.

The magnetic circuit of the high tension impulse transformer, describedherein, comprises a winding consisting of insulated layers of sheet ironof high permeability, the windings of which can be supported by aninternally arranged core, within the winding space of the primarywinding, and a further external casing to enclose the high voltagewinding.

A further characteristic of the invention is that the secondary windingis surrounded by a high volt-age cylindrical condenser, the inner foilof which is connected with the high voltage end of the secondary Windingwhilst the outer foil preferably is earthed.

If the high tension impulse transformer described above is directlymounted on a spark plug, the distance between the ends of the spark plugterminal and the end of the high voltage winding of the transformer canform an auxiliary spark gap.

Further particulars and characteristics of the invention are apparentfrom the following detailed description of the attached drawings, inwhich preferred forms of construction of the invention are shown by wayof example.

In the drawings accompanying this specification:

FIG. 1 is a diagram showing the switching arrangement of a condenserdischarging ignition installation for a four cylinder internalcombustion engine.

FIG. 2 is a vertical longitudinal section through a high tension impulsetransformer, combined with a spark plug, drawn to a larger scale.

FIG. 3 is a cross section through a part of one layer of the primarywinding of the transformer shown in FIGURE 2 considerably enlarged; and

FIG. 4 is a radial section through the secondary winding of thetransformer shown in FIG. 2 drawn to a larger scale.

The ignition arrangement diagrammatically shown in FIG. 1 consists of aDC. source, represented by the box 1, supplying electrical current at450 volts; a contact arrangement 2, shown in a frame of broken lines,which distributes the primary current to four high tension impulsetransformers 3, each of which is arranged on a cylinder of an internalcombustion engine.

The contact arrangement 2 includes a storage condenser Cl, which can,for instance, have a capacity of 6 ,wf. and provide full operating scopefor the ignition installation, i.e., four ignition impulses, withoutthereby lowering its voltage substantially.

Two further impulse condensers C2 and C3, connected in series, areconnected in parallel with the storage condenser Cl. The condensers C2,C3 each may have a capacity of about 0.5 f.

The junction of the two condensers C2, C3 is connected to the casing ofthe contact arrangement 2, that is, grounded. The other two terminals ofthe condensers C2, C3 respectively are connected to the ignitiondistributor contacts K1, K2 and K3, K4.

The high tension impulse transformers 3 are each enclosed in a groundedscreen. Each transformer 3 includes a primary winding 4 and a secondarywinding 5, a terminal of each of the windings 4 and 5 being earthed.

The high voltage end of each secondary winding 5 is earthed through astorage con-denser 6 and is also con- 3 nected to an electrode of aspark plug 7 having a grounded electrode.

The mode of operation of the ignition arrangement shown in FIG. 1 isobvious to the expert from the circuit. The contacts Kit to K4 areopened and closed in sequence by the ignition distributor. When eachcontact is closed, one of the impulse condensers C2, C3 is discharged.

When a contact is closed, not only does the discharging current flowfrom one condenser, but also the charging current of the other condenserflows at the same time through the primary winding of the impulsetransformer 3 concerned, thus the initial impulse is doubled. Thesequence of connect-ions, as such is known and was proposed as far backas the year 1938 by Hooven.

The structural arrangement of this impulse transformer is shown in FIG.2, from which it can be seen that it consists of a primary coil former8, a secondary coil former 9, a primary winding 10, a secondary winding11, -a high voltage condenser 12, an internal iron core 13, an externaliron shell 14 and a transformer casing 15.

The two coil formers 8 and 9 consists preferably of thermoplastics,those for the lower thermal ranges being made of polyethylene orpolyesters and those for higher thermal ranges being made, if necessary,of halogen polymerisates. The production can be carried out by injectionmoulding.

The primary coil former 8 consists of a tubular part having a radialarranged external flange 16, while the secondary coil former 9 is potshaped and contacts with the upper face of the flange 16 as well as atthe free end of the primary coil former 8, so that an enclosed windingspace is provided for the primary winding 10. The base of the secondarycoil former 9 is provided with a depending cylindrical projection 17,which fits into the interior of the primary coil former 8.

The upper end of the coil formers is closed by a lid 18, consisting ofthe same insulating material which lies in contact with the base of thesecondary coil former 9 and also serves to centralize the iron shell 14.

The inner iron core 13 is located inside the winding space for theprimary winding, the iron core 13 and iron shell 14- consisting of awinding comprising two or more layers of well insulated sheets of highpermeability iron.

The low voltage ends of the primary winding and the secondary winding 11are connected together within the space enclosed by the flange 16 andconnected with the earth terminal of the transformer. The high voltageend of the primary winding 10 is arranged within the space enclosed bythe flange 16 outside the iron shell 14, taken from the space for theprimary winding and connected with the terminal 19, which passes, bymeans of a glass bushing 20, through the upper cover 21 of thetransformer casing.

The high voltage electrode 22 of the secondary winding is located in thedepending cylindrical projection 17 of the secondary coil former 9.

In FIG. 2, the high voltage end of the secondary winding 11 is situatedat the top and the high voltage connection is, on the one hand,connected with the high voltage electrode 22 and, on the other hand,with the internal foil of the high voltage cylindrical condenser 12, theexternal foil of which is grounded.

The metal casing is hermetically sealed, the outer boundary of thecasing being formed by a cylindrical shell, the upper boundary by thelid 21 with the glass bushing 20, and the lower boundary by the flange16 or perhaps by the projection 17 with the high voltage electrode 22.

The high voltage electrode 22 of the transformer is so arranged that thedistance between it and the corresponding electrode 23 of the sparkingplug 24 is about 0.5 to 1.0 mm., in order to provide the auxiliary sparkgap required for reliable ignition.

The transformer is mounted in an adapter 25 of pressed sheet iron thathas the lower opening 26 which is constructed as a washer to becompressed, when the sparking plug 2'7 is screwed in place, so as toeffect perfect contact with the cylinder head 23, thus assuring a properseat for the transformer and at the same time providing a complete andefficient low resistance metal screen for the high voltage condensercircuit which carries steeply peaked and powerful impulses.

Such an effective screening is necessary in order to render the ignitionarrangement entirely free from interference in the decimeter wave range.Further, the described method of fixing renders the ignition arrangementwaterproof.

In the upper part of the high voltage transformer there is an evacuatedcapsule 31, of the kind used in aneroid barometers, to compensate forthe change in volume due to heat.

When settling the form of the primary winding 10 its ohmic resistanceshould be low relatively to its inductive resistance; further, thewindings should be closely coupled and well adapted to the load on thesecondary side, in relation to the aperiodic limit resistance.

Moreover, the inductive resistance of the primary winding should belarge, relatively to the inductive resistance of the connecting cablebetween the distributor contacts and the impulse transformer.

Taking into account these requirements and the permissible potential inthe winding to secure adequate insulation, a two-layer winding with aninternal diameter of 20 mm. and a length of 60 mm. was selected. In theinterior of the primary winding there is, to act as an iron core, awinding consisting of three or four layers of high permeability ironsheet 0.1 mm. thick, with adequate insulation between the layers.

The winding arranged on this core consists of a strip of copper foil 5mm. wide and 0.1 mm. thick. This strip of copper foil can be bare if itis insulated with a strip 29 of 30/,u plastics foil 10 mm. wideinterwound with it during winding.

This arrangement of the winding is shown diagrammatically in PEG. 3. Theinsulation between the layer consists of 3 layers of the same plasticsfoil. In the two layer arrangement with a total of ten turns the windingbegins and ends on the face of the flange 16 of the primary coil former.

As on account of the high instantaneous value of the impulse (450 v. a.equals 45 kw.) the electro dynamic stresses in the primary winding areconsiderable it is advisable to impregnate the insulating foil of theiron core as well as the Winding, prior to the winding with a solventfree, hardening plastics varnish and thereby fix the winding.

This assembly of the primary winding ensures, with suflicientconsideration of all other requirements, a minimum of radial expansionof the primary winding.

The construction of the secondary winding is shown in FIG. 4. Thesecondary winding 11 is shorter than the primary winding 10, andarranged to provide close coupling between each of the layers of thesecondary wind- 111g.

The arrangement of the secondary winding is based on the considerationthat with a potential of about 20 v. in thewinding, the insulation fromturn to turn of ordinary enarnelled wire is sufficient, but that theinsulation between the layers is not sufficient without the provision ofspecial means.

The secondary winding lll. also begins at the face of the flange 16 ofthe primary coil former. For the winding a wire of 0.07 mm. in diameterwith a coat of enamel about 0.01 mm. is employed. The 2,000 turnsselected here, as an example, are distributed over a total of tenlayers.

The first and second layers, the fifth and sixth layers, and the ninthand tenth layers progressively are wound from left to right according toFIG. 4, and have a length of 4.25 cm. each. The third and fourth layersas well as w the seventh and eighth layers are wound in the oppositedirection and have a length of 3.45 cm. each.

The maximum potential diflerence between the ends of two adjacent layersthat is possible amounts to about kv., starting with volt windingpotential. To insulate the layers two foils of plastics, with highpenetration resistance are employed.

As an example, a suitable foil is of polyethylene of thickness, whichhas a penetration resistance of 150 kv./ mm. In each layer the part notoccupied by the windings is filled up by a layer 30 of paper having athickness equal to the diameter of the wire.

Theseparate paper layers are treated in a manner that they do not impedethe penetration of the impregnating medium when completing thetransformer.

By means of the winding arrangement shown in FIG. 4, not only about 30%of the insulation space, while maintaining equal potential resistance,can be saved, but also the capacity of the winding itself can beconsiderably reduced compared with one of the usual multi layer coils.From the point of view of construction, this assembly also has theadvantage that several coils can be wound on the mandrel of an automaticcoil winding machine simultaneously.

The foil 12a on the high tension side of the high voltage condenser 12,consisting of a sheet of copper, is insulated against the uppermostlayer of the secondary winding 11 with the same number of layers ofinsulating material as the layers are insulated, the one from the other,while the number of layers of insulating material between the twocondenser foils is determined by the area of these foils and thecapacity required (about 40% of the energy content of a workingcondenser) on the low voltage side, the outer condenser foil preferablybeing earthed.

The iron shell 14 completes the external enclosure, as also is seen inFIGURE 2, which iron shell, similarly to the iron core 13, is composedof three or four layers of iron sheet having interposed insulating foil.

The above mentioned data show that in the high tension impulsetransformer described above, the insulating materials are used far moreeiiiciently than is usual in electro technical practice. Therefore, inorder to safeguard satislactory operation of the apparatus, the impulsetransformer must be constructed very carefully.

Above all, prior to impregnation, all dampness must be removed with thegreatest care. The windings must be exposed for asuflicient time toadequate vacuum, and it is advisable to effect a current heating fromthe interior outwards. it is also obvious that air pockets between different layers of foil must be avoided, as these, owing to the greatelectrical strength of field, rapidly destroy the organic insulatingsubstances by ionisation.

To avoid air pockets, the layers of foil tightly wound one over theother, can, before being used, becovered with a material such forinstance as petroleum jelly.

The inventionis not limited to the forms of construction described bythe way of example, and particularly the particular dimensions statedand also the electrical data are to be considered only as examples. Thescope of the present invention is given in the following patent claims:

What I claim is:

1. Ahigh tension ignition transformer for the production ofinstantaneous impulses, particularly for igniting fuel/ air mixtures,comprising a primary winding wound on an iron core supported by acylindrical former having an upper end and a lower end, a flangeprojecting radially outwards from said lower end and forming a base; asecondary winding of multiple layers surrounding the primary winding andsupported by a pot shaped former having a lower open portion in contactwith said base and whose upper portion is in contact with the upper endof the primary coil former and is provided with a depending cylindricalprojection extending inwardly of the primary coil former; the lowtension ends of the primary and secondary windings being grounded andbeing located in proximity to the flange while the high tension end ofthe secondary winding is disposed in the depending cylindricalprojection, one portion of each secondary winding layer being separatedby insulation from adjacent layers, another portion of said secondarywinding layers being overlapped by a portion of an adjacent overlappinglayer, each secondary layer being wound in a direction opposite to thepreceding underlapped layer, the last winding layer being joined to thewound capacitor.

2. A high tension ignition transformer for the production ofinstantaneous impulses, particularly for igniting tuel/ air mixtures,comprising a primary winding wound on aniron core supported by acylindrical former having an upper open end and a lower end, a flangeprojecting radially outwards from said lower end and forming a base; asecondary winding of multiple layers surrounding the primary winding andsupported by a pot shaped former whose lower open portion is in contactwith said base and whose upper portion is in contact with the upper endof the primary coil former and is provided with a depending cylindricalprojection extending inwardly of the primary coil former; the lowtension ends of the primary and secondary windings being grounded andbeing located in proximity to the flange while the high tension end ofthe secondary winding is disposed in the depending cylindricalprojection, the separate layers of the secondary winding being shorterin axial extension than the primary winding and being arranged instep-like formation relative to one another, extending towards the highvoltage end, one portion of each secondary winding layer being separatedby insulation from adjacent layers, another portion of said secondarywinding layers being overlapped by a portion of an adjacent overlappinglayer, each secondary layer being wound in a direction opposite to thepreced-j ing underlapped layer, the last winding layer being joined tothe wound capacitor..

3. A high tension ignition transformer for the production ofinstantaneous impulses, particularly for igniting fuel/ air mixtures,comprising a primary winding wound on an iron core supported by acylindrical former having an. upper end and a lower end, a flangeprojecting radially outwards from said lower end and forming a base; asecondary winding of multiple layers surrounding the primary winding andsupported by a pot shaped former whose lower portions is in contact withsaid base and whose upper portion is in contact with the upper end ofthe primary coil former and is provided with a depending cylindricalprojection extending inwardly of the primary coil former; the lowtension ends of the primary and secondary windings being grounded andbeing located in proximity to the flange while the high tension end ofthe secondary winding is disposed in the depending cylindricalprojection, said secondary winding consisting of wire layer portionsshorter in axial extension than said wire layer portion being arrangedin step-like formation relative toone another the primary windingtowards the high voltage end the unwound part of each layer being filledwith insulating material, the thickness of which is equal to thethickness of the wire layer portion, one portion of each secondarywinding layer being separated by insulation from adjacent layers,another portion of said secondary winding layers being overlapped by'aportion of an adjacent overlapping layer, each secondary layer beingwound in a direction opposite to the preceding underlapped layer, thelast winding layer been joined to the wound capacitor.

4. A high tension ignition transformer for the production ofinstantaneous impulses, particularly for igniting fuel/ air mixtures,comprising a primary winding wound on an iron core supported by acylindrical former having an upper end and a lower end, a flangeprojecting radially outwards and forming a base; a secondary winding ofmultiple layers surrounding the primary winding and supported by a potshaped former having a lower open portion in contact with said base andwhose upper portion is in contact with the upper end of the primary coilformer and is provided with a cylindrical projection extending inwardlyof the primary coil former; the low tension ends of the primary andsecondary windings being grounded and being located in proximity to theflange while the high tension end of the secondary winding is disposedin the depending cylindrical projection, said secondary windingconsisting of wire layer portions shorter in azial extension than theprimary winding said wire layer portions being arranged in step-likeformation relative to one another, towards the high voltage end theunwound part of each layer being filled with insulating material, thethickness of which is equal to the thickness of the wire layer portion,and each wire layer of the secondary winding being wound in oppositedirection to the direction of its adjacent wire layer so that thedirection of winding in the several layers alternates, one portion ofeach secondary winding layer being separated by insulation from adjacentlayers, another portion of said secondary winding layers beingoverlapped by a portion of an adjacent overlapping layer, each secondarylayer being wound in a direction opposite to the preceding underlappedlayer, the last winding layer been joined to the wound capacitor.

5. The invention as claimed in claim 3, wherein the wire layers of thesecondary winding are separated, the one from the other, over the wholelength of the coil by thin layers of insulating material.

6. The invention as claimed in claim 3, wherein the resistance of theprimary winding is less than the aperiodic limit resistance and isdefined by the formula 4L ye in which R is the resistance in ohms, L,the inductance of the circuit, C the capacity of the circuit.

7. The invention as claimed in claim 3, wherein the primary windingconsists of bare copper strip provided with a thin layer of insulatingmaterial.

8. The invention as claimed in claim 3, wherein the windings are withsynthetic resin varnish.

9. The invention as claimed in claim 3, wherein within the winding spacefor the primary winding, there is provided a core consisting ofinsulated layers of sheet iron of high permeability.

10. The invention as claimed in claim 3, wherein the primary andsecondary windings are surrounded by an external shell consisting ofinsulated layers of sheet iron of high permeability.

11. The invention as claimed in claim 3, wherein the primary andsecondary windings are surrounded by an external shell consisting ofinsulated layers of sheet iron of high permeability, said external shellhaving one end resting on said base of the former for the primarywinding and being centralised at the opposite end with a lid ofinsulating material.

12. The invention as claimed in claim 3, wherein the secondary windingis surrounded by a high tension cylindrical condenser, the inner foil ofwhich is connected with the high tension end of the secondary windingwhile the outer foil is grounded.

13. The invention as claimed in claim 3, wherein the internal space ofthe formers being so dimensioned that they can be mounted on theexterior of the insulator of a sparking plug.

14. A high tension ignition transformer for the production ofinstantaneous impulses, particularly for igniting fuel/ air mixtures,comprising a primary winding wound on an iron core supported by acylindrical former having an upper end and a lower end, a flangeprojecting radially outwards and forming a base; a secondary winding ofmultiple layers surrounding the primary winding and supported by a potshaped former having a lower open portion in contact with said base, andwhose upper portion is in contact with the upper is provided with acylindrical projection extending inwardly end of the primary coil formerand of the primary coil former; the low tension ends of the primarysecondary windings being grounded and being located in proximity to theflange while the high tension end of the secondary winding is disposedin the depending cylindrical projection, said secondary windingconsisting of wire layer portions, shorter in axial extension than theprimary winding said Wire layer portions being arranged in step-likeformation relative to one another, towards the high voltage end theunwound part of each layer being filled with insulating material, thethickness of which is equal to the thickness 'of the wire layer portion,the internal space of the formers being so dimensioned that they can bemounted on an exterior of the insulator of a sparking plug, with thehigh voltage end of the secondary located in the depending cylindricalprojection of the secondary coil former being spaced a predetermineddistance from the terminal of a sparking plug located in the interior ofthe former to form an auxiliary spark gap, one portion of each secondarywinding layer being separated by insulation from adjacent layers,another portion of said secondary winding layers being overlapped by aportion of an adjacent overlapping layer, each secondary layer beingwound in a direction opposite to the preceding underlapped layer, thelast winding layer being joined to the wound capacitor.

15. The invention as claimed in claim 3, wherein the transformer isenclosed in an air tight metal casing hermetically sealed and theconnection on the high voltage end of the primary winding is carriedco-axially through an insulator, out of a casing at the end remote tothe sparking plug opening.

16. The invention as claimed in claim 3, wherein an air tight casing forthe transformer contains an evacuated capsule.

17. The invention as claimed in claim 3, wherein the external casing ofthe transformer comprises an annular sheet iron adapter having a bottomflange, and an opening for a sparking plug in said base flange.

References Cited by the Examiner UNITED STATES PATENTS 1,633,047 6/27James 317-15762 1,869,233 7/32 Welter 336- 2,127,575 8/38 Thompson et al3l7157.6 2,328,443 8/43 Foster 33669 2,381,782 8/45 Stephens 336--702,394,768 2/46 Harkness 317-157.62 2,441,047 5/48 \Wall 317--l57.622,445,169 7/48 Frey 336-96 2,941,172 6/60 Sutton 336-92 2,972,713 2/61Sutton 336- 3,060,353 10/62 Shansky 33690 SAMUEL BERNSTEIN, PrimaryExaminer.

1. A HIGH TENSION IGNITION TRANSFORMER FOR THE PRODUCTION OFINSTANTANEOUS IMPULSES, PARTICULARLY FOR IGNITING FUEL/AIR MIXTURES,COMPRISING A PRIMARY WINDING WOUND ON AN IRON CORE SUPPORTED BY ACYLINDRICAL FORMER HAVING AN UPPER END AND A LOWER END, A FLANGEPROJECTING RADIALLY OUTWARDS FROM SAID LOWER END AND FORMING A BASE; ASECONDARY WINGING OF MULTIPLE LAYERS SURROUNDING THE PRIMARY WINDING ANDSUPPORTED BY A POT SHAPED FORMER HAVING A LOWER OPEN PORTION IN CONTACTWITH SAID BASE AND WHOSE UPPER PORTION IS CONTACT WITH THE UPPER END OFTHE PRIMARY COIL FORMER AND IS PROVIDED WITH A DEPENDING CYLINDRICALPROJECTION EXTENDING INWARDLY OF THE PRIMARY COIL FORMER; THE LOWERTENSION ENDS OF THE PRIMARY AND SECONDARY WINDINGS BEING GROUNDED ANDBEING LOCATED IN PROXIMITY TO THE FLANGE WHILE THE HIGH TENSION END OFTHE SECONDARY WINDING IS DISPOSED IN THE DEPENDING CYLINDRICALPROJECTION, ONE PORTION OF EACH SECONDARY WINDING LAYER BEING SEPARATEDBY INSULATION FROM ADJACENT LAYERS, ANOTHER PORTION OF SAID SECONDARYWINDING LAYERS BEING OVERLAPPED BY A PORTION OF AN ADJACENT OVERLAPPINGLAYER, EACH SECONDARY LAYER BEING WOUND IN A DIRECTION OPPOSITE TO THEPRECEDING UNDERLAPPED LAYER, THE LAST WINDING LAYER BEING JOINED TO THEWOUND CAPACITOR.